Tsunamis are usually triggered by earthquakes. The crust shifting is the primary effect; a knock-on (secondary) effect of this is the displacement of waterabove the moving crust. This is the start of a tsunami.
A normal, wind-driven wave may have the length of a 100m from crest to crest, but a tsunmai may be 200km in length. The heights also greatly differ: 2m for a normal wave versus 1m for a tsunami out at sea. Tsunamis move at speeds of around 800kph, rapidly approaching the coast almost unnoticed. As they near the land they slow, reduce in length and gain in height.
Japan Tsunami March 2011
Facts
The tsunami happened on Friday 11th March 14:46 Japan time
Tsunami was triggered by a magnitude 9 earthquake on the Richter Scale
Primary effects
Flooding of the land
Putting out fires
88,873 houses, 3,970 roads and 71 bridges destroyed
Over 15, 281 people died
Secondary effects
Radiation leak from the Fukishima nuclear power plant
Oyster fishing industry destroyed loss of jobs
Economic slow-down as companies like Toyota had to stop production
People leaving coastal towns forever due to fear of another tsunami
Large amounts of debris crossing the Pacific Ocean and potentially hitting the USA
Fires from burst gas pipes
Short-term responses
Putting out fires
People were rescued by helicopter
Companies such as Japan Emergency NGO started to rebuild houses
The Japanese Government have set an Aid budget of £2.8 billion
Temporary pre-fab houses set up in Rikuzentakata
Temporary schools set up
Long-term responses
Clearing the 20 million tonnes of debris from the tsunami
Tsunami detection and warning systems to be upgraded across the whole of the Pacific
The earthquake that caused the Boxing Day tsunami was estimated to be between 9.0 and 9.3 on the Richter scale - one of the largets earthquakes ever recorded. The tsunami then moved as a series of r'ipples' across the Indian Ocean which built up as massive waves when they aprroached the land. It was one of the worst natural diasters in history - nearly 300,000 people killed or disappeared completely. Loss of tourismt income as tourists stayed away from the effected areas.
Responses to the tsunami
Immediate responses
clean water, food, tents and plastic sheeting arrived as aid
$7 billion was donated worldwide for the affected countries
people in the UK donated £300 million (more than the government)
The UN's World Food Programme provided food and for more than 1.3 million people
Long-term responses
tsunami warning system - the disastrous effects of the Boxing Day tsunami led to the setting up of a tsunami early warning system in the Indian Ocean. Formal warnings are now sent to countries throughout the region if there's a tsunami threat. These warnings are then passed on to indvivduals via radio, television and e-mail or by bells, megaphones and loudspeakers attached to mosques
restoring mangrove swamps - the tourist industry in Thailand and Sri Lanka had grown rapidly before the tsunami. Many coastal areas had been cleared of mangrove swamps to make way for hotels.But mangroves act as a natural barrier - absorbing wave power and helping to protect coastlines and inland areas from tsunamis. After 2004, some projects to restore mangroves were started e.g. the Green Coast Project in Aceh, Indonesia. The new mangroves will help to increase the protection forfutrue tsunami, and also help to provide a livelihood for people affected by the 2004 tsunami, because mangroves are good breeding ground for fish.
How tsunamis form
Tsunamis are usually triggered by earthquakes. The crust shifting is the primary effect; a knock-on (secondary) effect of this is the displacement of waterabove the moving crust. This is the start of a tsunami.
A normal, wind-driven wave may have the length of a 100m from crest to crest, but a tsunmai may be 200km in length. The heights also greatly differ: 2m for a normal wave versus 1m for a tsunami out at sea. Tsunamis move at speeds of around 800kph, rapidly approaching the coast almost unnoticed. As they near the land they slow, reduce in length and gain in height.
Japan Tsunami March 2011
Facts
Primary effects
Secondary effects
Short-term responses
Long-term responses
A collection of excellent BBC videos:
The Asian Tsunami: Causes and effects - http://www.bbc.co.uk/learningzone/clips/the-asian-tsunami-causes-and-effects/3195.html
The Asian Tsunami: Damage to coral reefs - http://www.bbc.co.uk/learningzone/clips/the-asian-tsunami-damage-to-coral-reefs/3200.html
The Asian Tsunami: Disease - http://www.bbc.co.uk/learningzone/clips/the-asian-tsunami-disease/3197.html
The Asian Tsunami: Effects on tourism - http://www.bbc.co.uk/learningzone/clips/the-asian-tsunami-effects-on-tourism/3201.html
The Asian Tsunami: Eyewitness accounts in Sri Lanka - http://www.bbc.co.uk/learningzone/clips/the-asian-tsunami-eyewitness-accounts-in-sri-lanka/3198.html
The Asian Tsunami: Predicting a future event - http://www.bbc.co.uk/learningzone/clips/the-asian-tsunami-predicting-a-future-event/3203.html
The Asian Tsunami: Variable impacts - http://www.bbc.co.uk/learningzone/clips/the-asian-tsunami-variable-impacts/3202.html
Awesome series of animations - http://library.thinkquest.org/04oct/01724/causes_sum.html
The effects of the Boxing Day tsunami 2004
The earthquake that caused the Boxing Day tsunami was estimated to be between 9.0 and 9.3 on the Richter scale - one of the largets earthquakes ever recorded. The tsunami then moved as a series of r'ipples' across the Indian Ocean which built up as massive waves when they aprroached the land. It was one of the worst natural diasters in history - nearly 300,000 people killed or disappeared completely. Loss of tourismt income as tourists stayed away from the effected areas.
Responses to the tsunami
Immediate responses
Long-term responses